1. Field of the Invention
This invention relates to a process for the production of acylhydrazones of the formyl-acetic acid ester, which are suitable as starting materials for the preparation of 1,2,3-thiadiazole derivatives.
2. Brief Description of the Background of the Invention Including Prior Art
Formyl-acetic acid ethyl ester semicarbazone (W. Wislicenus, H. W. Bywaters, Liebigs Annalen der Chemie Vol. 356, page 50 [1907]) and formyl-acetic acid ethyl ester-ethoxycarbonylhydrazone (R. Raap, R. G. Micetich, Canadian Journal of Chemistry, Vol. 46, page 1057 [1968]) are already known from the literature. Both compounds are produced by a process wherein the sodium salt of the formyl-acetic acid ester is reacted with corresponding hydrazine derivatives.
A precondition of this process is the synthesis and isolation of the formyl-acetic acid ester sodium salt. This can however only be produced via complicated and extended work processes in unsatisfactory yields (German Pat. No. 708,513; Great Britain Pat. No. 568,512; U.S.P. 2,394,255, W. Deuschel, Helv. Chim. Acta vol. 35, page 1587 [1952]).
One process (L. Beer and P. Halbig, German Pat. No. 708,513) condenses formic acid ester and acetic acid ester with sodium alcoholate in an autoclave reaction, wherein the acetic acid ester is produced from the excess alcohol by pressurizing with carbon monoxide.
This process is unsuitable for an economic technical production in view of the poor yields and of the equipment expenditures for the pressure reaction. The yields listed in the literature cannot be reproduced.
In another process (E. H. Northey, Great Britain Pat. No. 568,512; U.S. Pat. No. 2,394,255) acetic acid ester and formic acid ester are condensed with alcoholfree sodium alcoholate by employing carbon monoxide under pressure. Again this process is unsuitable for industrial production based on the required autoclave reaction and the insufficient yields.
A third process (W. Deuscherl, Helv. Chim. Acta vol. 35, page 1587 [1952]) condenses a mixture of acetic acid ester and formic acid ester with alcoholfree sodium alcoholate produced from powderized sodium and alcohol in ether. Based on the employment of suspensions of sodium in ether and in view of the poor yields, this process is at best limited to laboratory work, but is completely unsuitable for a technical production.